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Cellular Reproduction Overview: Why Reproduce?

This text provides an overview of cellular reproduction, discussing the reasons why organisms reproduce and the stages of the cell cycle, including interphase and mitosis.

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Cellular Reproduction Overview: Why Reproduce?

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  1. Cell Biology I. Overview II. Membranes: How Matter Get in and Out of Cells III. Cellular Respiration IV. Photosynthesis V. Protein Synthesis VI. Cellular Reproduction

  2. VII. CELL REPRODUCTION Overview: Why Reproduce?

  3. VII. CELL REPRODUCTION Overview: Why Reproduce? Reproduction is selected for, by definition. X X X X

  4. - WHY?? Bigger is better…. So selection favors growth… But as cells increase in size, they decrease in efficiency.

  5. - WHY?? Bigger is better…. So selection favors growth… But as cells increase in size, they decrease in efficiency. So, to get bigger, most organisms increase cell number, not cell size….

  6. - WHY?? And with many cells, cell specialization can increase efficiency at the organismal level.

  7. VII. CELL REPRODUCTION Overview: Why Reproduce? A. The Cell Cycle INTERPHASE S (DNA synthesis) LE 12-5 G1 Mitosis Cytokinesis G2 MITOTIC (M) PHASE

  8. VII. CELL REPRODUCTION Overview: Why Reproduce? A. The Cell Cycle     1.  Interphase: a.  G1: high metabolic activity (protein synthesis) chromosomes diffuse; one DNA double helix per chromosome

  9. LE 12-15 G0 G1 checkpoint G1 G1 If a cell does not receive a go-ahead signal at the G1 checkpoint, the cell exits the cell cycle and goes into G0, a nondividing state. If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle.

  10. VII. CELL REPRODUCTION Overview: Why Reproduce? A. The Cell Cycle     1.  Interphase a. G1 b. S Chromosome duplication (including DNA synthesis) A C C G T G G C Centromere A C C G T G G C A C C G T G G C Two identical double-helices, each composed of an ‘old’ and ‘new’ strand. Creating two chromatids in each chromosome Sister chromatids

  11. VII. CELL REPRODUCTION Overview: Why Reproduce? A. The Cell Cycle     1.  Interphase a. G1 b. S c. G2

  12. VII. CELL REPRODUCTION Overview: Why Reproduce? A. The Cell Cycle     1.  Interphase 2. Mitosis

  13. INTERPHASE PROPHASE PROMETAPHASE Kinetochore Centrosomes (with centriole pairs Early mitotic spindle Chromatin (duplicated) Aster Fragments of nuclear envelope Nonkinetochore microtubules Centromere LE 12-6aa Nucleus Plasma membrane Chromosome, consisting of two sister chromatids Kinetochore microtubule Nuclear envelope

  14. METAPHASE ANAPHASE TELOPHASE Nucleolus forming Metaphase plate Cleavage furrow LE 12-6ba Nuclear envelope forming Centrosome at one spindle pole Daughter chromosomes Spindle

  15. VII. CELL REPRODUCTION Overview: Why Reproduce? A. The Cell Cycle B. DNA Replication C. Mitosis G2 OF INTERPHASE PROPHASE PROMETAPHASE

  16. VII. CELL REPRODUCTION Overview: Why Reproduce? A. The Cell Cycle B. DNA Replication C. Mitosis LE 12-6da TELOPHASE AND CYTOKINESIS METAPHASE ANAPHASE

  17. VII. CELL REPRODUCTION Overview: Why Reproduce? A. The Cell Cycle B. DNA Replication C. Mitosis 10 µm LE 12-10 Nucleus Chromatin condensing Chromosomes Nucleolus Cell plate Prometaphase. We now see discrete chromosomes; each consists of two identical sister chromatids. Later in prometaphase, the nuclear envelope will fragment. Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at the metaphase plate. Anaphase. The chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of the cell as their kinetochore micro- tubules shorten. Prophase. The chromatin is condensing. The nucleolus is beginning to disappear. Although not yet visible in the micrograph, the mitotic spindle is starting to form. Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.

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